Cathode ray tubes (CRTs) may display raster images having non-linear and geometric distortion. This is because the CRTs create asymmetrical coil deflection by introducing non-linear and geometric distortion of the current field and horizontal scans.
To overcome the non-linear and geometric distortion, some devices predistort the image such that the CRTs display the predistorted image without distortion. These devices often change the field and horizontal scanning voltage wave using analog circuitry. More precisely, these processing devices change the current in the deflection coil according to a predistortion wave voltage. For example, a parabolic predistortion wave voltage may correct pincushion distortion, an exponential predistortion wave voltage may correct non-linear distortion, and an S predistortion wave voltage may correct extension distortion.
But these devices' analog circuitry often does not sufficiently improve image quality for advanced, multiple mode, digital televisions. Not only are these devices' analog circuitry ineffective at significantly reducing distortion, they are complex, costly, and consume large amounts of power.